So far, an organic resist material has been mainly used for applying micro-processing to optical devices, magnetic devices, semiconductor devices and others. The organic resist material, having the general versatility, has been widely used in a field of photolithography. However, the organic resist material, being high in molecular weight, has a problem in that a pattern at a boundary portion of an exposed portion and an unexposed portion tends to be obscure. Furthermore, since light or an electron beam is directly used for recording, it has been difficult to form a fine pattern smaller than a spot diameter of light or an electron beam.
On the other hand, an inorganic resist material, being smaller in molecular weight, has an advantage in that a pattern at a boundary portion of an exposed portion and an unexposed portion is clear. Accordingly, various researches are under way of the inorganic resist materials at present. For instance, Patent Document 1 discloses a method where a portion of a particular crystalline state of a chalcogen compound is selectively removed by making use of difference of etching rates due to difference of crystalline states of a chalcogen compound, to obtain an optical information recording medium master.
In the Patent Document 1, a method where heat generated by light exposure or the like is used to vary a crystalline state of a chalcogen compound is used, which method is called a heat mode recording. In the heat mode recording, only a portion where a temperature reaches or exceeds a certain threshold value causes a change in physical and chemical states and a portion where a temperature does not reach a threshold value, does not cause the change in physical and chemical states even when the portion is heated; accordingly, a clear pattern can be advantageously formed. Furthermore, in the heat mode recording, among a portion that is exposed to light or an electron beam, only a portion where a temperature reaches or exceeds a threshold value causes a change of state. Accordingly, a pattern finer than a spot diameter of light or an electron beam can be advantageously formed.
Furthermore, Patent Document 2 discloses a producing method of a master of optical information recording media, which uses the heat mode recording. It is described in the document that, according to the method, disposing a recording auxiliary layer besides a resist film may result in improved recording sensitivity and an effectively controlled etching shape after recording.
On the other hand, Patent Document 3 discloses a resist material that uses an incomplete oxide of a transition metal such as W or Mo as a resist film. In the Patent Document 3, it is intended to obtain fine patterns with an existing exposing device by making use of absorption of UV-ray or visible light of the incomplete oxide.
However, there is a problem in that each of the resist materials described in Patent Documents 1 to 3 tends to be insufficient in the sensitivity to light or an electron beam since the decomposition temperature thereof is high. Furthermore, Patent Document 2 studies to provide a recording auxiliary layer from the viewpoint of improving the recording sensitivity. However, there are objections that the number of processes increases and a layer structure becomes complicated when the recording auxiliary layer is disposed.
Furthermore, when an electron beam is used for recording, other problems occurs in some cases, where an electron beam penetrates toward a substrate without reacting with a resist material, or it causes a need for disposing a material such as electroconductive metal on a substrate or a substrate top surface in order to avoid charges of electrons. However, a countermeasure for that is not disclosed.
Patent Document 1: Japanese Patent Application Laid-Open No. 10-97738
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-11489
Patent Document 3: Japanese Patent Application Laid-Open No. 2003-315988